Characterisation and role of <i>Isoamylase1 (Meisa1</i>) gene in cassava

Abstract

The current concept for starch biosynthesis in plants is that amylopectin, the major fraction of starch, is synthesised by the concerted actions of ADP-Glc pyrophosphorylase (AGPase), soluble starch synthase (SS), starch-branching enzyme (BE), and starch-debranching enzyme (DBE). We have isolated a cDNA clone of Isoamylase1 gene, a member of DBE family from cassava (Manihot esculenta Crantz) storage root. The cloned cDNA fragment sequence (764 bp) showed high identity of 90% to Rcisa1, and 81% identity to Psisa1, Stisa1 and Atisa1. The deduced protein sequence showed highest (92%) identity with RCISA1. The comparative sequence analysis confirmed the cloned fragment to be M. esculenta isoamylase1 gene (Meisa1; accession number GU229751). Genomic analysis revealed occurrence of at least two copies of the Meisa1 gene. Highest Meisa1 transcript expression levels were detected in fibrous root followed by in the stem and least detected in the leaf and petiole. Analysis of the temporal expression pattern in the storage root showed initial and maximum expression at 90 days after planting (DAP), and declined thereafter to undetectable levels by 180 DAP. The results implicate a major role of Meisa1 in storage root differentiation and early starch granule initiation.

Molecular characterization of genes encoding isoamylase-type debranching enzyme in tuberous root of sweet potato, <i>Ipomoea batatas</i> (L.) Lam.

“…However, few studies have focused on tuberous root plants, such as cassava, sweet potato, and yam, which store their starch in roots (Beyene et al 2010;Kim et al 2005). In this study, we isolated three genes encoding IbISA1, IbISA2, and IbISA3 from one of the tuberous root plants, sweet potato (Ipomoea batatas (L.)).…”

“…The expression of ISAs in relation to seed development has been investigated in several plant species, including rice, maize, barley, rye and amaranths (Kubo et al 2010;Ohdan et al 2005;Park et al 2014;Sun et al 1999;Zheng et al 2013). However, in the case of tuberous root species, sweet potato (Convolvulaceae), cassava (Euphorbiaceae), and yam (Dioscoreaceae) (Scott et al 2000), there are few reports of cloned and characterized ISAs (Beyene et al 2010;Kim et al 2005). Furthermore, the relationship between gene expression of ISAs and sink development is not well understood in tuberous root plants.…”

An Analysis of Partial DNA Sequence of Meisa1 Gene on Sweet and Bitter Cassavas (Manihot esculenta Crantz.)

“…Meisa1 gene begins to be expressed when the plant is three months old after planting and then the expression is stoped when the plant is six months old, and its highest level of expression occurs in tuber followed by the stem, leaf, and petiole. It indicates that Meisa1 gene has a major role in root differentiation to become storage root or tuber and early initiation of starch granule formation (Beyene et al 2010).…”

“…Complement DNA (cDNA) encoding ISA1 from cassava (better known as Meisal gen) has been cloned and characterized by Beyene et al (2010) and may reach 764 bp in length. Meisa1 gene begins to be expressed when the plant is three months old after planting and then the expression is stoped when the plant is six months old, and its highest level of expression occurs in tuber followed by the stem, leaf, and petiole.…”

“…ISA1, ISA2, and ISA3 and each type respectively has a specific function in starch metabolism (Sundberg et al 2013;Kang et al 2013). Genes encoding isoamylase-type 1 (ISA1) have been cloned and characterized from some of crop species (Sun et al 1999;Kim et al 2005;Takashima et al 2007;Beyene et al 2010).…”